[Bug middle-end/59409] [4.9 Regression] 253.perlbmk in SPEC CPU 2K is miscompiled

[hjl.tools at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59409

--- Comment #18 from H.J. Lu <hjl.tools at gmail dot com> ---
(In reply to H.J. Lu from comment #17)
> Perl_my_bcopy (len=31, to=0xf7fd801d "\021q", from=0x8023f0 "\264\005q")
> is miscompiled when inlined:
> 
> Old value = 19935280
> New value = 808464432
> Perl_my_bcopy (len=-1, to=0xf7fd803c "\260Vx", from=<optimized out>) at
> util.c:1559
> 1559		while (len--)
> 
> The last write is to 4-bytes at 0xf7fd803b:
> 
>   442dd7:       83 fe 0b                cmp    $0xb,%esi
>   442dda:       67 44 88 42 0b          mov    %r8b,0xb(%edx)

It is OK since it is a byte store.

>   442ddf:       74 27                   je     442e08 <Perl_pp_rv2av+0x898>
> 
> (gdb) p/x $edx
> $300 = 0xf7fd8030
> (gdb) p/x $edx + 0xb
> $301 = 0xf7fd803b
> (gdb) 
> 
> But the last byte should be written at 0xf7fd801d + 30 == 0xf7fd803b.
> There are 3 byte overflow for write.  I will see if I can write a
> testcase.